Friday, April 18, 2008

DailyTech - The Megahertz Race is Now Officially the Multi-core Race

The next major milestone for the CPU engineers comes late this year, with the debut of 45nm Shanghai. Shanghai, for all intents and purposes, is nearly identical to the B3 stepping of Socket 1207 Opteron (Barcelona) shipping today. However, where as Barcelona had its HyperTransport 3.0 clock generator fused off, Shanghai will once again attempt to get HT3.0 right.

"Don't be disappointed, AMD is making up for it," hints one engineer. Further conversations revealed that inter-CPU communication is going to be a big deal with the 45nm refresh. The first breadcrumb comes with a new "native six-core" Shanghai derivative, currently codenamed Istanbul. This processor is clearly targeted at Intel's recently announced six-core, 45nm Dunnington processor.

A twin-die Istanbul processor could enable 12 cores in a single package. Each of these cores will communicate to each other via the now-enabled HT3.0 interconnect on the processor.

The rabbit hole gets deeper. Since each of these processors will contain a dual-channel memory controller, a single-core can emulate quad-channel memory functions by accessing the other dual-channel memory controller on the same socket. This move is likely a preemptive strike against Intel's Nehalem tri-channel memory controller.

Motherboard manufacturers claim Shanghai and its many-core derivatives will be backwards compatible with existing Socket 1207 motherboards. However, processor-to-processor communication will downgrade to lower HyperTransport frequencies on these older motherboards. The newest 1207+ motherboards will officially support the HyperTransport 3.0 frequencies.